In recent years, public healthcare expenditures are rising, and hence reduction of healthcare expenditures is the government's and public's great concern. The doctor's fees for diseases due to lifestyle related diseases account for one-third of the public healthcare expenditures. Under such circumstances, reduction of public health care expenditures, improvement of health expectancy, and improvement of QOL (Quality of Life) are demanded, and to meet such demands, specific medical examinations have been implemented, and a concept of “very early stages of disease” has been widely spread.
In particular, it is known that metabolic syndrome, which is a subject of screening in specific medical examinations, develops diabetes, dyslipidemia, high blood pressure caused by insulin resistance due to accumulation of visceral fat obesity, and it is expected that early detection of metabolic syndrome will lead to prevention of disease progression and improvement of QOL, and further, reduction of public health care expenditures.
Insulin resistance is important for early detection of lifestyle related diseases as described above; however, the only way of specific medical examinations has been measurement of abdominal girth for estimation of the risk of insulin resistance.
In recent years, a close relationship between insulin resistance and postprandial hyperlipidemia has been revealed, and a possibility that postprandial hyperlipidemia is the cause of insulin resistance has been pointed out, and therefore, postprandial hyperlipidemia can be recognized to be a metabolic error of an origin of metabolic syndrome. As such, postprandial hyperlipidemia is attracting attention not only as a factor for detecting an initial stage of metabolic syndrome (very early stages of diseases), but also as a risk factor of arteriosclerosis. For example, it can be said that when the triglyceride concentration in a non-fasting state is high, the risk of developing coronary heart disease is high.
However, diagnosis of postprandial hyperlipidemia requires observation of variation in lipid concentration in blood during 6 to 10 hours after eating. That is, to measure the state of hyperlipidemia after eating, it is required to hold examinees for about 6 to 10 hours to collect blood multiple times, but such an operation can be implemented only in clinical research and cannot be practically implemented in clinical sites.
In addition, with increasing public health consciousness, specified functional foods that inhibit fat absorption and the like are coming into practical use, and consciousness of dietary ingestion of fat is rising. Although the people are conscious to blood lipid, there is no health management apparatus for easily measuring blood lipid at home. One reason for this is that blood collection itself is restricted by the Medical Practitioners' Act, and even if there is no such restriction, examination apparatuses are not available in the price range for ordinary families. Furthermore, there are problems such as disposal of waste liquid, and long analysis time.
Under such circumstances, the following techniques relating to a blood component measurement method have been proposed.
For example, Japanese Patent Application Laid-Open No. 2004-251673 (PTL 1) discloses a technique relating to an apparatus that calculates the concentration of a measurement object by outputting and emitting light having a wavelength of a near-infrared region and an infrared region with an acoustic optical variable vibration filter to a living body, and by analyzing and computing an absorption spectrum obtained by receiving light that has transmitted through a measurement object or reflected by the measurement object. That is, the technique disclosed in PTL 1 is directed to calculate the amount of absorbed light and the like from the difference between the amount of emitted light and the amount of received light and the like by utilizing a phenomenon in which light is absorbed by blood component, to thereby calculate the blood component concentration from the results of the calculation.
In addition, Japanese Patent Application Laid-Open No. 2010-66280 (PTL 2) discloses a technique relating to a quantitative apparatus for analyzing glucose concentration including: a near-infrared light source; a detection means that detects near-infrared light; a guiding means that introduces near-infrared light emitted by the near-infrared light source to a biological tissue or bodily fluid and guides near-infrared light passing through or deffusely reflected by the biological tissue or the bodily fluid to the detection means; and a computing means that performs a regression analysis of the glucose concentration based on signals obtained by the detection means. The computing means carries out quantification using continuous spectrum signals obtained by continuously measuring wavelengths in at least three adjacent wavelength regions as defined below as explanatory variables, and the glucose concentration as a criterion variable; a first wavelength region is in a range of 1,550 to 1,650 nm to measure absorption derived from OH groups in a glucose molecule, a second wavelength region is in a range of 1,480 to 1,550 nm to measure absorption derived from NH groups in a biological component, and a third wavelength region is in a range of 1,650 to 1,880 nm to measure absorption derived from CH groups in the biological component, within the wavelength region from 1,480 to 1,880 nm in which harmonics of a first harmonic tone is observed, and in which the effect of water absorption is relatively small. That is, as with the technique disclosed in PTL 1, the technique disclosed in PTL 2 utilizes a phenomenon in which light is absorbed by the NH group, CH group and OH group of glucose to calculate the amount of absorbed light from the difference between the amount of emitted light and the amount of received light and the like, to thereby calculate the concentration of the blood component from the results of the calculation.
Further, Japanese Patent Application Laid-Open No. 2002-168775 (PTL 3) discloses a technique relating to a rapid measuring method of a plasma component of a mammal by spectrum information in a visual and near-infrared region, which is characterized by measuring an absorbance in the visual and near-infrared region having a wavelength of 400-2,500 nm by using a near-infrared spectrophotometer relative to separated plasma in measuring the plasma component of the mammal, calculating a primary differential and a secondary differential of the absorbance, using the absorbance, and the primary differential and the secondary differential of the absorbance in the visual and near-infrared region as independent variables, selecting independent variables to the number of two to ten having high explanation power from among the independent variables, predicting triglyceride, inorganic phosphorus, potassium, lactate dehydrogenase and an albumin-globulin ratio in the plasma from the information on the independent variables having high explanation power, and realizing measurement based on the predicted values. That is, as with the techniques of PTL 1 and PTL 2, the technique of PTL 3 utilizes a phenomenon in which plasma absorbs visible light having wavelengths of 400-2500 nm and light of a near-infrared region to calculate the triglyceride concentration and the like in plasma from the difference between the amount of emitted light and the amount of received light and the like.